The present invention relates generally to apparatus for removing residual concrete from the interior of a concrete mixing drum, and more particularly to apparatus including an elongate probe supported for axial movement into and out of an open end of the drum, preferably automatically, and including at least one nozzle positioned for discharging fluid under pressure against difficult to access interior surfaces of the drum, particularly surfaces on helical ribs or flights facing away from the open end of the drum, on which surfaces concrete tends to cure and accumulate, for dislodging and removing the concrete.
Ready-mix concrete trucks have a rotatable drum for holding a quantity of ready-mix concrete. The drum typically includes several raised helical ribs or flights extending around its interior surfaces. These ribs act to mix the concrete when the drum is rotated in one direction, and when the drum is rotated in the opposite direction, the ribs lift the concrete to an elevated opening, either at the front or rear of the drum, through which the concrete is discharged from the drum. Over the course of operation, concrete has been found to accumulate on the surfaces in the drum, particularly on the rib surfaces facing away from the open end of the drum. This concrete, if left in place to cure and harden, has been found to decrease the effectiveness of the ribs for both mixing and lifting the concrete, and adds weight to the truck. The concrete, if allowed to accumulate, will also lessen the capacity of the drum. Therefore, it is common practice, at the end of each day, or more often, to wash the interior of the drum. However, the washing typically requires as much as 300 gallons of water, and still has been found to be ineffective at removing the accumulated concrete from the surfaces of the ribs facing opposite the open end of the drum, especially if the concrete is allowed to cure and harden.
Reference Steinke U.S. Pat. No. 5,244,498 issued Sep. 14, 1993 to W.R. Grace and Co. of Canada Limited; and Hailey U.S. Pat. No. 5,507,875 issued Apr. 16, 1996, which disclose various known apparatus and methods for cleaning concrete mixing drums. More particularly, Steinke teaches manual insertion of a hand held elongate probe into a concrete mixing drum for spraying a set retarding agent against the residual concrete on the inner surface of the drum for removing the concrete. Hailey discloses utilizing a vibration impact device applied against the exterior of the concrete mixing drum for loosening and dislodging the accumulated concrete.
Shortcomings of relying on a retarding agent such as disclosed in Steinke for ridding a concrete mixing drum of residual concrete include observed ineffectiveness of the retarding agents under a variety of environmental conditions such as elevated temperatures. Additionally, the retarding agents have been found to be generally ineffective for removing concrete that has largely or mostly cured. Limitations of using hand held devices like the Steinke probe include unwieldiness when fully extended into a drum, particularly when using pressurized fluids. Also, it is unsafe to rotate the drum when any hand held device is used therein.
Shortcomings of vibrational methods of cleaning concrete mixing drums such as disclosed in Hailey include the noise generated by the vibrating devices and the time required. Further, it has been found that the known cleaning apparatus and methods often still leave sufficient residual concrete on the interior surfaces of the drum so as to require periodic manual cleaning.
Manual cleaning typically involves a worker entering the drum, and, using a water hose and hand tools as required, loosening the concrete from the drum surfaces and washing the concrete pieces to the bottom of the drum. Then, the worker exits the drum, and the drum is rotated so as to discharge the cleaning water and concrete pieces from the drum. Shortcomings here include the possibility of the worker being injured while entering or exiting the drum, which requires a ladder or similar means, or from slipping or falling on the wet surfaces in the drum. The worker can also be injured by loosened pieces of concrete which can fall from the upper surfaces in the drum. Also, it is noisy in the drum during the cleaning operation as a jackhammer, sledge hammer or similar device is typically used to beat the concrete off of the interior surfaces.
Accordingly, the present invention is directed to overcoming one or more of the shortcomings as discussed above.
In one embodiment of the present invention, an apparatus for removing concrete from the interior surfaces of a concrete mixing drum is disclosed, the drum including an open end and at least one interior surface facing away from or opposite the open end, the apparatus comprising an elongate probe having a longitudinal axis and an axially extending forward end adapted for insertion into the drum through the open end thereof; a vertically adjustable support structure supporting a guideway support, the guideway support including at least one bearing adapted for supporting the probe for movement of the forward end thereof into and out of the drum through the open end thereof; and at least one fluid nozzle mounted to the probe in position for discharging a stream of fluid against the at least one interior surface facing opposite the open end under sufficient pressure to dislodge accumulated concrete therefrom as the probe is moved in the drum.
In a preferred method of operation, the elongate probe of the apparatus is positioned for insertion of the forward end thereof into the open end of the drum. The probe can then be axially moved into the drum and the fluid under pressure delivered through the fluid conduit to the nozzle for discharging the stream of fluid under pressure against the interior drum surface for dislodging the concrete. During this time, the drum is rotated in the discharge direction and the probe is moved axially into or out of the drum such that the interior surfaces thereof, most importantly the surfaces of the helical ribs or flights facing away from the open end of the drum, are reached by the stream of fluid. Then, once the probe has traversed essentially the length of the drum, the probe is withdrawn from the drum, and the concrete removal operation is complete when the dislodged material is discharged from the drum.
In a preferred aspect of the invention, at least four fluid nozzles are provided at different positions adjacent the end of the probe for discharging the streams of fluid under pressure in different directions, the preferred fluid stream being a pencil shaped stream, although solid cone shaped streams, hollow cone shaped streams, and fan shaped streams, can likewise be used.
Here, is should be recognized that the fluid stream can comprise any material effective for dislodging accumulated concrete from the drum surfaces, including, but not limited to, liquids such as water either alone or including a detergent, gritty matter or the like which can be introduced into the fluid stream after discharge from the nozzle; and cryogenic materials such as pelletized dry ice, and the like.